A rocker arm of the pre-cited type is known from DE-A 26 52 154. In this case, the cap is configured as a flat disc which is secured in axial direction in the reception bore by a circlip. The outer diameter of the disc and the diameter of the reception bore are matched to each other so that a narrow annular gap is formed therebetween through which air can escape to the exterior. Further, the hollow inner piston of the valve clearance compensation element is provided on its end with slots, or radially extending grooves are provided in the end face of the disc facing the inner piston. The two last-mentioned means are intended to permit the pressure medium which flows from the oil supply bore at first into an annular space to flow further into the oil reservoir. A drawback of this arrangement is that the cap can become displaced radially to the extent that a vent gap is formed only in a certain edge region. Depending on the position of this gap and the position the rocker arm or the finger lever takes during the standstill of the internal combustion piston engine, so much pressure medium can escape from the valve clearance compensation element through this vent gap that the operation of the valve clearance compensation element is not guaranteed at first on a re-starting of the internal combustion piston engine. In addition, the oil serving as the pressure medium can flow out through the guide gap between the valve clearance compensation element and the peripheral surface of the reception bore. Moreover, the fact that grooves have to be made in the disc, or slots stamped into the inner piston, increases the costs of manufacture.